Causes for a speaker to go open circuit??

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Seegs, Jul 23, 2005.

  1. Seegs

    Seegs Member

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    I've had a Eminence Cannabis Rex in my 64 Deluxe and after changing power amp tubes yesterday I heard this wierd growling and scrathing sound and then nothing...

    I checked the resistance on my speaker and it read open...I put a Weber 12150F in there...changed the speaker cable just in case and it works fine...

    Could a shorted speaker cable cause the speaker to go open like that...bad output transformer or maybe just a defective speaker...??

    Any ideas would be helpful!!

    Chow,
    Seegs
     
  2. John Phillips

    John Phillips Member

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    Defective speaker or too much power.

    That's it.

    No fault on a tube amp can blow a speaker, because the speaker is isolated from the amp's circuit by the OT, and the secondary winding of the OT - the only bit that's actually connected to the speaker - is in fact a passive component.

    (A solid-state amp is different, and a shorted output transistor can easily blow a speaker by connecting it directly to the DC power supply.)

    A bad speaker cable can seriously damage an amp, but not a speaker.

    Remember that amps peak well above their rated RMS power usually though, and some speaker makers are more conservative than others about how they rate them - Celestion's definition seems to be 'a cranked tube amp of the same power' (ie possibly as much as double the RMS power they're quoting); Eminence's seems to be less.

    Even so, I don't think a 22W amp could blow a speaker rated at 50W in normal use (or even with bass through it, which reduces the effective power handling), so I'd guess you have a faulty speaker.
     
  3. Seegs

    Seegs Member

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    Thanks John...I was hoping it was just a freak thing...I will order another one and hope it lasts longer...I have another CR in my 30-40 watt Fargen Dual classic that gets played more often and driven way harder than the speaker in my Deluxe did and it's fine...

    So maybe I was just unlucky...!!

    Chow,
    Seegs
     
  4. Trevor Bond

    Trevor Bond Guest

    Several things... Heat... marginal manufacturing... square wave slammin the cone...
     
  5. Wakarusa

    Wakarusa Member

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    Depending on how long you've had it, Eminence may replace it under warranty
     

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